Summary A Cessna 172, registration N8522U, serial number 17252422, was en route from Arlington, Washington, to Nanaimo, British Columbia. The aircraft was flying under visual flight rules (VFR) at 4500feet above sea level on a northwesterly heading. On initial contact, the Victoria, British Columbia, terminal airspace (YYJ) terminal controller assigned a transponder code, radar identified the flight, and approved the flight to proceed as requested to Nanaimo. About one minute later, a West Coast Air de Havilland DHC-6 (TwinOtter), call signC606, serial number94, checked in with the YYJ terminal controller. The Twin Otter was radar identified and approved to proceed to Victoria Harbour at 4500feet above sea level on a south-southwesterly heading. Another controller reported for duty at this time. The first transmission received by the new controller when he took over the Victoria VFR traffic advisory frequency was an advisory from the Cessna pilot stating that he was descending because of a Twin Otter. At about 1018 Pacific daylight time, the Cessna and the Twin Otter came into proximity of each other, necessitating evasive action by the Cessna pilot. The Twin Otter pilot did not see the Cessna in time to take evasive action. Ce rapport est galement disponible en franais. Other Factual Information The Victoria, British Columbia, airport weather conditions recorded about 30minutes before the occurrence indicated high, thin, overcast clouds and unlimited visibility. The weather was sunny and is not considered to have contributed to this occurrence. The Cessna pilot held a valid Airline Transport Pilot License and a current medical certificate, both issued by the US Federal Aviation Administration. This licence is recognized in Canada. The pilot had accumulated about 10400total flying hours, of which about 1500hours were on the Cessna172. The previous day, the pilot had worked a standard 7.5-hour duty day, with normal rest time. In the 90days before the incident, he had flown 15 hours, including 5.5hours in the previous 30days. The Cessna was equipped with external lighting consisting of navigation lights, a rotating beacon, and two landing lights mounted on the left wing leading edge. Only the rotating beacon was on at the time of the occurrence. The aircraft was equipped with a transponder but did not have a traffic alert and collision-avoidance system (TCAS). The front-seat passenger of the Cessna spotted the Twin Otter off the right wing tip and advised the pilot. The evasive manoeuvre consisted of rapidly descending about 200feet straight ahead in a wings-level attitude and returning to 4500feet. The flight continued on to Nanaimo as planned.1 The Twin Otter, flown by the captain, had departed Vancouver Harbour on the operator's regularly scheduled visual flight rules (VFR) flight117 to Victoria. The crew contacted the Victoria terminal airspace (YYJ) terminal controller about 10nautical miles (nm) south of Vancouver International Airport, when the aircraft was level at 4500feet above sea level. The Twin Otter was radar identified and approved to continue to Victoria Harbour. When the Twin Otter captain saw the conflicting Cessna, the Cessna was already in the evasive descent and passing in front of and below the Twin Otter. No evasive action was taken by the crew of the Twin Otter. During this event, the Twin Otter co-pilot had been occupied with cockpit duties and never did establish visual contact with the Cessna. The Twin Otter was equipped with external lighting consisting of navigation lights, a rotating beacon, and two pulse-type landing lights, one mounted in the leading edge of each wing (modified to incorporate a pulse function that continually turns each light on and off in an alternating fashion). The operator's standard operating procedures require that the landing/pulse lights remain on from before take-off until after landing. The aircraft was equipped with a transponder but did not have a TCAS. The Twin Otter captain held a valid Airline Transport Pilot Licence and a current aviation medical certificate. The medical certificate had a restriction requiring glasses to be worn; the pilot was wearing his glasses at the time. The captain had accumulated about 32000total flying hours, including about 17000hours on the Twin Otter. In the previous 48hours, he had about 10hours' flight time and about 23hours' duty time. In the previous 90days, he had 97hours' flight time. The pilot's Twin Otter pilot proficiency check was valid until 01May2000. He did not have a current instrument flight rating, nor was one required for this operation. The Twin Otter co-pilot held a valid Commercial Pilot Licence and a current aviation medical certificate. He had accumulated about 1200total flying hours, including 60hours on the Twin Otter. In the previous 48hours, he had 5hours' flight time and 12hours' duty time. In the previous 90days, about 60hours of flight time were recorded. The co-pilot's Twin Otter pilot proficiency check was valid until 01April2001. His instrument flight rating was valid until 01March2001, subject to currency requirements. This incident has been identified as an air proximity event. No conditions were identified that would have interfered with normal aircraft operation. Technical examinations of the aircraft and their components were therefore not carried out. The Nav Canada Area Control Centre in Vancouver is responsible for providing air traffic control (ATC) services in the airspace where this event occurred. Sometime before the day shift started at 0630, the midnight duty shift manager was advised that two controllers would not be present for their shifts2. The shift manager therefore revised the day shift schedule and decided not to withdraw a controller from a scheduled training course in the building that day. The revised schedule ensured that at least three people would be on shift at any given time; the original schedule called for three to six people at various times throughout the day. To mitigate the staffing and workload problem, traffic restrictions were placed in effect that would limit the number of instrument flight rules (IFR) training aircraft to two within the combined YYJ/YCD sectors until 1000. A fourth controller was not scheduled to arrive until 1015. At 0630, the YYJ terminal controller, who was the acting shift supervisor, arrived and performed a functions review, which included a staffing-level assessment. He also reviewed the traffic restrictions that were in effect. The shift supervisor mistakenly believed that a fourth controller would arrive at 1000 rather than at 1015 as scheduled (due to minimum rest requirements). The shift supervisor must ensure adequate staffing levels, so he discussed the situation with the other two controllers on duty at 0630. They considered the traffic restrictions already in place to mitigate the staffing situation and decided to proceed with the current plan. Consequently, as of 0700, the unit would have three controllers on shift (including the shift supervisor) when four were scheduled, and as of 0900, the unit would still have three controllers on shift when five were scheduled. If a shift supervisor feels that the staffing level is inadequate, he/she must report the concerns to the duty shift manager and attempt to resolve the issue. At 0700, a qualified controller reported to work to sign in, as normal, before going elsewhere in the building for his training course. Because of the shortage of staff, the shift supervisor requested this controller to withdraw from the training course and work a control position. The request was denied by the midnight shift manager, who was still present although he was not the current duty shift manager. The current duty shift manager was not notified of the request, and the request was not repeated. After 0900, the unit was staffed with three controllers when five were originally scheduled. The established relief break routine continued, with each controller working for about one hour and then taking a break of about 30minutes. At 1000, four events occurred: one controller was on a break, leaving two controllers active, in accordance with the established routine; the fourth controller did not arrive as expected (mistakenly) by the shift supervisor; the traffic restrictions ended, as planned; and the normal IFR traffic workload and complexity was increasing. A search of the TSB database identified 40 Air Traffic Services-related investigations between 1990 and 2000 in which the shift supervisor was working a control position at the time of the occurrence. Sometime between 1000 and 1015, the shift supervisor expressed his concern to his colleague about the late arrival of the fourth controller. It was at this time that he became aware that the fourth controller was not scheduled until 1015. Although the workload was increasing, the shift supervisor did not recall the third controller from his break to assist, nor did he exercise other options to control his workload, such as requesting tower controllers in Victoria and Vancouver to reduce their departure rates for aircraft proceeding into his airspace, cancelling the provision of radar service to training aircraft at Nanaimo, or cancelling radar service to VFR aircraft already in his airspace and directing them to descend below the floor of the YYJ VFR traffic advisory (VTA). At 1009, the YYJ terminal controller was contacted by the Cessna pilot. In the process of radar identifying the aircraft, the controller recorded the time, aircraft registration, aircraft type, destination, route, and altitude on the VFR Traffic Record. At about 1010, the YYJ terminal controller was contacted by the Twin Otter pilot, who was about 10nm south of Vancouver International Airport. The controller recorded the same information for the Twin Otter as for the Cessna on the same traffic record sheet. He did not make any notation to serve as a reminder that these aircraft required further attention. At 1015, the fourth controller arrived in accordance with the revised schedule. The shift supervisor requested the arriving controller to take over the YYJ VTA sector so that he (the shift supervisor) could focus on the IFR traffic at Victoria and Nanaimo. The combined YYJ terminal position was busy at the time, and the prescribed handoff briefing could not be coordinated or completed. The arriving controller began the equipment transfer process to open the VTA position, intending to accept VTA traffic from the shift supervisor as he was able to hand off control of each aircraft. The arriving controller was just taking his position at 1018 when he received an advisory transmission from the Cessna pilot, who had to descend because of a Twin Otter. The shift supervisor did not hear the transmission from the Cessna because he was no longer monitoring the VTA frequency. No traffic advisories were directed to any of the aircraft involved in the occurrence. The YYJ terminal controller was also serving as the acting shift supervisor for the Victoria terminal complex. He held a valid ATC licence and had qualified in the Victoria complex of the Vancouver Area Control Centre in 1996. He was working his sixth day shift after six days off. In the previous 48hours, he had worked 8.5hours each day and had finished at 1500 on the day before the occurrence. Records indicate that he had not received training to work in a supervisory capacity, nor is such training provided. On the day of the occurrence, his day shift as the acting shift supervisor began at 0630. The controller was working an equal share of the time with other controllers in an active control position, which is reported to be a normal situation. Before the incident time of 1018, the controller had been on duty for 3 hours 48 minutes. The personnel utilization record shows that the controller had taken two breaks; however, he could not recall having taken a break. Canadian airspace is divided into seven classes, one of which is Class C airspace. The airspace may be divided further into different types of controlled airspace, one of which is the terminal control area (TCA). A TCA is established at high-traffic airports to provide a control service. TCA operating rules are established by the classification of the airspace within the TCA. Aeronautical Information Publication (AIP), section RAC (Rules of the Air and Air Traffic Services) 2.8.3, describes Class C airspace: Class C airspace is a controlled airspace within which both IFR and VFR flights are permitted, but VFR flights require a clearance from ATC to enter. ATC separation is provided between all aircraft operating under IFR and, as necessary to resolve possible conflicts, between VFR and IFR aircraft. Aircraft will be provided with traffic information. Conflict resolution will be provided, upon request, after VFR aircraft is provided with traffic information. AIP, section RAC 2.5.1, states: the see and be seen principle of VFR separation cannot always provide positive separation. Accordingly, in certain airspace and at certain altitudes VFR flight is either prohibited or subject to specific restrictions prior to entry and during flight. This incident occurred within the Victoria TCA, which is designated as ClassC airspace. Within this airspace, ATC is obligated to provide traffic advisory information to assist pilots in seeing and avoiding other aircraft to minimize the risk of conflict or collision. Radar is the primary tool used by controllers in the Victoria TCA to monitor traffic and ensure that adequate separation is maintained between IFR aircraft. It is also used to determine when traffic advisories are required to prevent conflicts involving VFR aircraft. Radar by itself may not provide enough information to the controller to highlight potential aircraft conflicts under all circumstances. Other tools that help controllers maintain situational awareness of aircraft traffic include flight progress strip marking and handling procedures, progress strip board design and management, and various radar display tools and scanning techniques. In Air Traffic Services Bulletin #ATSI-8709, Nav Canada recommends cocking of flight progress strips to serve as reminders of flights that require further attention. In this procedure, controllers lift (cock) one end of an individual plastic holder so that it protrudes above the others. These holders, stacked in order on a slanted board, each contain a strip of paper with a record of data pertaining to an IFR flight. Flight progress strips, however, are not used in the Victoria terminal complex for tracking VFR flights. Rather, the VFR Traffic Record, a separate single sheet of paper, is used to record VFR traffic. Interviews of controllers did not reveal a common or recommended procedure used on this record for tracking flights in a continually changing environment or for identifying flights that require further attention.